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Monday, August 28, 2017

Diatom of the Month - August 2017: Fragilariforma virescens

vivien August 28, 2017 0

post by David Williams*

Although he never wrote it down, the late Colin Patterson, one time vertebrate palaeontologist at my home from home, the Natural History Museum, London, often said that when confronted with any particular biological specimen, three questions should come into the minds of systematists: What is it? What is it related to? Where does it live?

For me, the first is often a struggle, as wading through books of images can be a tad soul-destroying, especially if the images never quite match what’s in front of you. Start with something easy – that’s what Frank Round told me, a long while ago now. Easy? There’s a lovely book by Archie Carr, A Naturalist in Florida, A Celebration of Eden (1994). In it there’s a key to the fishes of Alachua County, Florida, first published in 1941. One instruction reads: “Not as above; fins with dangerous spines; catfish-like—in fact, a catfish”, with a footnote: “Any damned fool knows a catfish”. So, Frank suggested Fragilaria virescens1 because, well you’ve guessed already: “Any damned fool knows Fragilaria virescens.”

Fig. 1. BM 81303: Tunbridge Wells, syntype of Fragilaria virescens. a) BM 81303: Tunbridge Wells, LM. b) Tunbridge Wells, SEM: Internal valve. c) Tunbridge Wells, SEM: Girdle of whole frustule. d) Tunbridge Wells, SEM: Valves connected with spines. e) From Ralfs, J. 1843, Annals and Magazine of Natural History 12: fig. 6.

I was lucky enough to have access in the Natural History Museum, London (NHM) diatom collections to more material supposedly of this species than I could deal with in a reasonable amount of time, upwards of 500 plus slides, most from localities in the UK, but many more from Europe, some from the USA, others from Australia. At that time, I didn’t look at nearly enough specimens, but it was obvious to me after a short while that, no, “Any damned fool would not know Fragilaria virescens”.

Fig. 2. River Stort in Southeast England (17^thSept. 2011, https://en.wikipedia.org/wiki/River_Stort).

Fragilaria virescens is normally considered a common, cosmopolitan species, found often, found everywhere. But after looking at just a few specimens from outside the UK, I became aware that this name had become attached to anything that vaguely looked like its potted description. Here’s one from an online key: “Valves with linear or slightly convex margins, narrowing to rostrate or cuneate apices”. I’m responsible for another, perhaps even simpler, description. I guess it’s best to look at the pictures. But looking at the specimens (rather than pictures) in the NHM, it became clear I wasn’t dealing with one species but a quite a number, some already with names, others in need of one. I also had access to Ralf’s original specimens, which helps. So the “What is it?” question was hard to answer straight away but I came to the conclusion, not yet fully documented I should add, that Fragilaria virescensis anything but a cosmopolitan species – from the material I have had access to, it occurs only in the UK, and some parts of Europe – a different species extends upwards into Lapland, for example, and most of the specimens from Australia, along with others from further far-flung territories, were simple misidentifications. So, the answer to “Where does it live?” emerged from investigating “What is it?”.

Now we have a much better understanding of the species, with its rectangular frustules, the linear colonies it forms, the valve being lanceolate to linear with tapering, rostrate to capitate apices. We now know that it has a fairly faint central sternum, and that the mantle margin has siliceous plaques. The linear colonies are a result of spines on the valve face/mantle border, which are simple interlocking projections. There are apical pore fields at both poles and one polar rimoportula. Its girdle (cingulum) has 4 to 6 open bands, and the plastids are numerous small discs; and we also know a little about its ‘development’, from auxospore to vegetative valve. From this constellation of characters, some define the species, others the genus; the thin barely visible sternum, a character of the genus – but it is not a Fragilaria (whatever that might be). So the answer to the question “What is it related to?” is: other members of the genus Fragilariforma, having this barely visible sternum. Since Ralfs described it in 1843, Fragilaria virescenshas been sub-divided a number of times, yielding some 80+ names of varieties and forms. Resolution of these names (“What are they?”) might be achieved to a certain degree by examining the type specimens of each, should they still be available. But a comparative collection, like that in the NHM, is a far better way, assessing numerous specimens, from many geographical regions.

Taking an apparently well-known diatom (“Any damned fool knows Fragilaria virescens”) and investigating it closely tells us that we actually didn’t know what it was, what it was related to, nor where it lived? I think we have a better idea now. Let me finish with a few more wise words from Colin Patterson, and these are published: “ […] you never know enough about anything, and if for a few months or years you should ever believe that you do, you are either past it or in for a surprise…Yesterday’s secure knowledge is tomorrow’s laughing matter”.

*Diatom systematist-taxonomist at the Natural History Museum, London, UK

1. The genus Fragilariforma typified by F. virescens was described by Williams and Round (1988).

Patterson, C. (2011) Adventures in the fish trade. Zootaxa 2946: 118–136. [edited and with an introduction by D. M. Williams and A. C. Gill]

Williams, D.M. (2001) Comments on the structure of ‘post-auxospore’ valves of Fragilariforma virescens. In: Lange–Bertalot Festschrift, Studies on diatoms (Jahn, R., Kociolek, J.P., Witkowski, A. & Compe`re, P., editors), 103–117. A.R.G. Gantner, Germany.
Williams, D.M. and Round, F.E. (1988). Fragilariforma, nom. nov., a new generic name for Neofragilaria Williams & Round. Diatom Research 3: 265-267.

Tags # Algae # Diatoms # Systematics Continue Reading

Monday, July 24, 2017

Diatom of the Month - July 2017: New discoveries await!

vivien July 24, 2017 0

In the last year and a half, ten different authors have talked about 19 diatom species from 19 different genera in our “Diatom of the Month” blog series (11 biraphid, 2 araphid, 2 centric, 1 epithemioid, 1 eunotioid, 1 monoraphid, and 1 nitzschioid), and we got to know about some fantastic 2D and 3D diatom art. We reached thousands of people online via social media (see image below), thus raising awareness about these beautiful and extremely useful primary producers and environmental indicators.

We importantly relied on the wonderful “Diatoms of the United States” resource for reference and inspiration, which has so far produced taxon pages for 155 genera (25 are underway), and 851 species (202 are underway)! This was made possible over the years by more than 110 taxon contributors, an effort led by Marina Potapova, Sarah Spaulding, and Mark Edlund and kept under scrutiny by the review board members. The DOTUS Facebook page provides regular updates and features as well as news about course like the Summer Field Courses in Iowa on ecology and systematics of diatoms, ecology and systematics of algae, ecology of algal blooms, and even an introductory course for high school students!

New discoveries on the world of diatoms keep taking place. For example, the “Diatoms from remote places” project led by Loren Bahls, curator of the Montana Diatom Collectionand funded by Adventurers and Scientists for Conservation has found 67 new and rare diatom taxa (belonging to over 20 genera).Volunteer collections comprise specimens from all of western North America’s major biomes —arctic tundra, boreal forest, temperate rainforest, deserts, alpine tundra, montane forest, and steppe—and all the samples are from remote, relatively unspoiled habitats. This initiative allowed to reveal that the central Cascades in Oregon is a diatom species diversity hotspot. And surely cool new discoveries about diatoms in lakes, rivers, streams, wetlands everywhere will emerge at the upcoming North American Diatom Symposium (Sep 27 - Oct 1) at the Stone Laboratory on Gibraltar Island in Lake Eerie!

The ~20,000 diatom taxa discovered / described by humans is only the tip of the diatom biodiversity iceberg! Believe it or not there may be up to 2-10 million species of diatom on Earth, with scientists still trying to better define "what a diatom species is" (Guiry, 2012). So many new species are yet to be discovered that citizen scientists, volunteers, and aficionados are very much needed to collect, preserve and study them, in the Everglades (see periphyton mats in the image below) and anywhere else where there is a little bit of water or moisture for some diatoms (and/or other algae) to survive.

Stay tuned and do not forget that these invisible organisms ‘paved the way’ for many other species on this planet (and, who knows, maybe beyond…)!

Guiry, M.D. (2012). How many species of algae are there? Journal of phycology 48: 1057-1063.

Spaulding, S.A., Lubinski, D.J. and Potapova, M. (2010). Diatoms of the United States. http://westerndiatoms.colorado.edu. Accessed on 24 July, 2017.

Tags # Algae # Conferences # Diatoms Continue Reading

Thursday, June 22, 2017

Diatom of the Month – June 2017: Fragilaria synegrotesca

vivien June 22, 2017 0

by Nick Schulte*

I think Fragilaria synegrotesca is a cute diatom. Although long and lanky (nothing wrong with that!), F. synegrotesca has an adorable, sometimes very slight, potbelly (Fig. 1).

Fig. 1. a) Live frustules in a rosette colony (http://fcelter.fiu.edu/data/database/diatom/index.htm?species=3568)

b) Fragilaria synegrotesca in valve view (Schulte 2014).

Now, some boring diatomist (e.g., me) might describe that little bump in the middle right as “a unilaterally expanded, hyaline central margin” and that’s accurate enough. But I also like to think of it as F. synegrotesca’s belly pooch. It brings to my mind the potbellies of seahorses, pigs, puppies and toddlers, and it seems very boop-able.

But let’s move past the physical attributes of this diatom, as the allure of this species is in its “actions”. Fragilaria synegrotesca has so far only been reported from karstic wetlands of the Caribbean and is most well-known from the Florida Everglades. In the Everglades, F. synegrotesca is nearly ubiquitous (Fig. 2), and it’s one of the five most abundant species in the calcareous periphyton mats in the nutrient-poor freshwater marshes (Gaiser et al. 2006).

Fig. 2. Relative abundance (%) of F. synegrotesca across the Everglades (data from the Comprehensive Everglades Restoration Plan Monitoring and Assessment Plan).

A major issue in Everglades restoration is getting the amounts of water and nutrients that enter this wetland right. Every winter/spring (the “dry season”), sloughs and inundated prairies often dry down. This happens more often and more severely now than in the “natural” pre-drainage state in many sites. But water managers (e.g., the South Florida Water Management District) can’t just send water through the marshes unless it’s “clean” (e.g., low in phosphorus), so as not to harm organisms that are adapted to this wetland’s low nutrient waters. So, Everglades restoration is between a bit of a rock and a hard place: we need to deliver more water to help the organisms that need high water (and can’t handle severe dry-down – e.g., many fish), but not at the expense of the organisms that can’t handle high nutrients in the water (e.g., some grasses and sedges).

Fragilaria synegrotesca is one of those organisms that doesn’t like to be dried out (Gottlieb et al. 2005, Lee et al. 2013), and its preference for being wet makes it a potentially “reliable indicator of the absence of periodic drying” in the ‘Glades (Gaiser et al. 2011). We can therefore use the abundance of this species (alongside other indicators) to measure the effects on biodiversity that potential reduced water flow might have upon different locations. This information can then inform decisions on how much water should be sent where and when – all key questions in Everglades restoration.

Unlike its freshwater-loving, high nutrient-hating buddies Brachysira microcephala, Encyonema evergladianum, and Mastogloia calcarea (let’s call them the “Fresh Diatoms of Belle Glades,” or “Freshies” for short), F. synegrotesca can also live comfortably in moderate phosphorus (P) concentrations and slightly salty water (“oligohaline”).

So, we can think of F. synegrotesca as that close friend that is too cool for us sometimes and likes to hang out with hipper, more indulgent folks.

And if this diatom is found in relatively high abundance in the absence of the Freshies, we know that area might be getting a little too phosphorus-y and/or salty than is normal. Now, there are some regions of the Everglades where finding F. synegrotescain enriched or salty places is normal, but by now we know which places are “normally” enriched/salty and which are not. So, if we see this species hanging out with the Salty Boys or the +P Posse in the good side of town (i.e., a normally freshwater, low nutrient place), we know something’s about to go down. In this way, I guess F. synegrotesca is also like that sweet suburban kid who gets caught up in the wrong crowd, and we’d rather see it back at home with the Freshies.

But here is some science to back up these potentially confusing analogies. In the Everglades, the total phosphorus (TP) optimum of F. synegrotesca is 270±202 µg P g^-1periphtyon (Gaiser et al. 2006), and this species has been designated as an indicator of high TP (La Hée and Gaiser 2012). Compare that to oligotrophic, freshwater indicators (B. microcephala, E. evergladianum, and M. calcarea) that have a mean TP optimum of 159 µg g^-1 (Gaiser et al. 2006). Our diatom of the month also has a salinity optimum and tolerance of 5±7.3 ppt (parts per thousand) – slightly higher than the Freshies (mean optimum across those 3 taxa = 2.9 ppt) (Wachnicka et al. 2010). Importantly, though, F. synegrotesca is generally not an indicator of a nutrient or salinity impacted site. Rather, its presence might indicate that a place is in limbo: it’s not too far gone, but it’s worse than we would expect if everything was OK. And F. synegrotesca alone doesn’t tell us much: rather, we have to look at the entire community of diatoms (and other algae and cyanobacteria) in order to make sense of the ecological impacts of modified nutrient levels and hydrology. So we use an “indicator community” analysis approach rather than “indicator species.”

As an example, in the Comprehensive Everglades Restoration Plan (CERP) Monitoring and Assessment Program (MAP) scientists from the Gaiser and Trexler labs report on how ~150 sites across the Everglades (and their animals, plants, and algae in periphyton mats) are affected by nutrient enrichment. To do this, one of the best measurements of site alteration is a combined periphyton TP-diatom community composition metric (RECOVER 2014, see pages 6-33 – 6-39). They use a “stoplight” reporting technique: green means baseline (“success”) conditions (TP < 200 µg / g), yellow means “caution” (TP = 200-250 µg / g), and red means “altered” (TP > 250 µg / g) (Fig. 3). Fragilaria synegrotesca is one of the diatoms that can contribute to a “caution” designation if it’s found away from the Freshies.

Fig. 3. Condition status of sampling sites from 2011 using a periphtyon TP-diatom community metric (from RECOVER 2014; Fig. 6-17).

So, while F. synegrotesca may seem a bit pudgy, it is a mover and shaker of the diatom scene in the Everglades. In the Everglades, there is the potential for more widespread dry-downs, human-caused phosphorus enrichment in the Everglades interior (particularly in the northern Everglades and near canals), and for sea-level rise in the southern Everglades (pushing saltier, nutrient-enriched water into the freshwater inland regions). Fragilaria synegrotesca and its associated community are great tools to understand how such disturbances are affecting the nature of this wonderful and important wetland. The ongoing diligent scientific monitoring and analysis (e.g., by CERP MAP and the Florida Coastal Everglades Long Term Ecological Research program) allow us to understand things like a potbellied diatom that inform sustainable management and conservation of the entire ecosystem.

*Ph.D. student at the Institute of Arctic and Alpine Research, University of Colorado Boulder and FIU Algae Research Lab alumnus

Gaiser, E. E., Childers, D. L., Jones, R. D., Richards, J. H., Scinto, L. J., & Trexler, J. C. (2006). Periphyton responses to eutrophication in the Florida Everglades: Cross‐system patterns of structural and compositional change. Limnology and Oceanography, 51(1part2), 617-630.

Gaiser, E. E., McCormick, P. V., Hagerthey, S. E., & Gottlieb, A. D. (2011). Landscape patterns of periphyton in the Florida Everglades. Critical Reviews in Environmental Science and Technology, 41(S1), 92-120.

Gottlieb, A., Richards, J., & Gaiser, E. (2005). Effects of desiccation duration on the community structure and nutrient retention of short and long-hydroperiod Everglades periphyton mats. Aquatic Botany, 82(2), 99-112.

Lee, S. S., Gaiser, E. E., & Trexler, J. C. (2013). Diatom-based models for inferring hydrology and periphyton abundance in a subtropical karstic wetland: Implications for ecosystem-scale bioassessment. Wetlands, 33(1), 157-173.

RECOVER (2014). System Status Report. Comprehensive Everglades Restoration Plan, Restoration Coordination and Verification (RECOVER). U.S. Army Corps of Engineers Jacksonville District, Jacksonville, Florida, and South Florida Water Management District, West Palm Beach, Florida, USA. http://141.232.10.32/pm/ssr_2014/cerp_ssr_2014.aspx

Schulte, N. (2014). Fragilaria synegrotesca. In Diatoms of the United States. Retrieved June 16, 2017, from http://westerndiatoms.colorado.edu/taxa/species/fragilaria_synegrotesca

Wachnicka, A., Gaiser, E., Collins, L., Frankovich, T., & Boyer, J. (2010). Distribution of diatoms and development of diatom-based models for inferring salinity and nutrient concentrations in Florida Bay and adjacent coastal wetlands of south Florida (USA). Estuaries and Coasts, 33(5), 1080-1098.

Tags # Algae # Diatoms # Everglades Continue Reading

Monday, May 22, 2017

Diatom of the Month – May 2017: Navicula lanceolata

vivien May 22, 2017 0

by Martyn Kelly*, in collaboration with Luca Marazzi

Navicula lanceolata (Agardh) Ehrenberg 1838 is a symmetrical biraphid diatom with lanceolate valve margins, broad in the central valve and slightly rostrate, rounded ends (Fig. 1, #1); the central area is an irregular oval (Fig. 1, #2), and striae are radiate, except at the ends where they become convergent (Fig. 1, #3). This species has two chloroplasts, one along each side of the girdle (Fig. 2) and is highly motile.

Fig. 1. Navicula lanceolata (Source: http://westerndiatoms.colorado.edu/taxa/species/Navicula_lanceolata).

Fig. 2. Navicula lanceolata in fresh samples with brown chloroplasts (Source: http://craticula.ncl.ac.uk/EADiatomKey/html/taxon13521390.html;

Image Copyright: E.J. Cox).

This is one of the most widely-distributed and frequently-encountered diatoms in both Europe and North America and is particularly abundant in winter and early spring; like a few other motile diatoms, it can form dark-brown patches on the top of biofilms (Fig. 3) visible to the naked eye. It can be abundant in streams and rivers that are relatively unpolluted, but it also thrives in water that is quite heavily enriched with both nutrients and organic pollution. N. lanceolata however is not found in very soft or acidic water and is much less common in lakes.

Fig. 3. Dark brown patches of Navicula lanceolata on the top surface of a cobble collected from Thropton Burn, Northumberland in early spring (with a pound coin to indicate scale).

Although this broad tolerance of environmental conditions is often interpreted as an indication that there may be genetic variation and, perhaps, cryptic or semi-cryptic species lurking within the traditional description, this does not seem to be the case for this species (M. Kelly, D. Mann, S. Sato, unpublished data, based on variation in the rbcL gene). That previous sentence should probably be re-cast as “a wide range of the chemical conditions that ecologists worry about” because Navicula lanceolata is almost certainly as choosy as any organism about the conditions where it thrives. It is just that the variables that we use to represent “pollution” do not feature strongly in the life choices of this particular species. It also confuses us by thriving at the time of year when many ecologists in the northern hemisphere are hunkered down in their laboratories and offices rather than out in the field. But anyone who is prepared to head out to a stream on a winter’s day when river levels are low and plunge their hand into the freezing water is likely to be surprised by the thickness of the biofilm relative to what we expect in the summer. If stones are fairly well embedded into the streambed, the algae that grow on their upper surface are not that vulnerable to being scoured off by high current velocities, as there is a “boundary layer” just above the stone where friction reduces the current velocity substantially. Also, at this time of year, invertebrate grazers are less active and so this is a period when algae which can cope with cool water thrive.

Fig. 4. The underwater landscape of the River Wear (Co. Durham, UK) in February, with individual motile cells of Navicula lanceolatamoving through “bushes” of Gomphonema olivaceum. There are also some cells of Achnanthidium minutissimum in the foreground and a filament of Ulothrix zonata in the background. For more examples of illustrations such as this see www.martynkelly.co.uk.

Life in a thick biofilm, however, creates its own problems. For example, abundant algae, bacteria and particulate matter block out the little winter sunlight that filters through the water to the stream bed. Being a motile organism has clear advantages, allowing N. lanceolata to move through the biofilm to the surface layers where it can harvest this sunlight. This species is one of a small number of diatoms (Navicula bottnica, an estuarine diatom, is another) that seem to aggregate to form distinct dark brown patches on the top of submerged biofilms (see Fig. 3). If you scrape a small part of one of these patches from the rock and examine it under the microscope, you will see a near monoculture of one of these species.

That these dark brown patches of diatoms live on top of a submerged biofilm suggests that we should take account of the organization of organisms within a biofilm as well as simply listing all the species that we find. However, the standard means of sampling a stone are too coarse to preserve such subtleties. A biochemist is interested not just in what amino acids constitute a protein, but how these are organized, because it is this that determines their function. In the same way, the organisms that inhabit microscopic biofilms are not distributed randomly within those biofilms. Moving beyond making lists of species is, however, far from straightforward. Some such as Lothar Geitler have achieved this using cytological preparations of carefully-collected material (Mann, 2015). Others have used scanning electron microscopy to similar ends (Rimet et al., 2009). My approach has been to try to recreate the three-dimensional form of biofilms using paint and pencil (Kelly, 2012). Fig. 4 shows a reconstruction of the type of microhabitat where I find Navicula lanceolata in the rivers of northern England. The long stalks associated with Gomphonema olivaceum and ‘relatives’ creates a matrix within which motile Naviculaand Nitzschia species can move in order to make the most of the resources that the habitat has to offer. As the months pass and the water warms, so invertebrates become more active and graze away the biofilm until, by May, it will consist mostly of Achnanthidium minutissimum and ‘relatives’ which form a microscopic “pasture” on which caddis and chironomid larvae graze.

Diatomists interpret ecology in terms of spatial distribution in relation to chemical variables. But Navicula lanceolata is a good example of a species whose distribution depends as much on physical and biological factors (e.g. cool conditions and a thick biofilm) as it does on water chemistry. There are, undoubtedly, many other diatoms in our rivers that have similarly rich stories to tell. Poring over the minutiae of diatom frustules has yielded much useful information over the years, but many of the secrets of this group of algae are lost as soon as we souse them in oxidizing agents. This species serves as a good reminder that studying diatoms in their live state often yields precious additional insights into their ecology.

* Partner, Bowburn Consultancy

Kelly, M.G. (2012). The semiotics of slime: visual representation of phytobenthos as an aid to understanding ecological status. Freshwater Reviews 5: 105-119.

Mann, D.G. (2015). Unconventional diatom collections. Nova Hedwigia Beiheft 144: 35-59.

Rimet, F., Ector, L., Cauchie, H.-M. & Hofmann, L. (2009). Changes in diatom-dominated biofilms during simulated improvements in water quality: implications for diatom-based monitoring in rivers. European Journal of Phycology 44: 567-577.

Tags # Diatoms # Rivers # Streams Continue Reading

Thursday, March 16, 2017

Diatom of the month: March 2017 - Mastogloia pseudosmithii

vivien March 16, 2017 0

by Sylvia Lee, FIU & Periphyton lab alumna

Did you know that March 19 is Taxonomist Appreciation Day?

Fig. 1. Cartoon on what taxonomy is. Image credit: BuzzHootRoor from https://smallpondscience.com/2014/03/19/today-is-taxonomist-appreciation-day/

Taxonomy is the study of organisms and their classification (or in more witty/punny terms in the image above, “how you phylum”). Recognizing and putting names to organisms may come easy to some natural-born naturalists, but taxonomy can be a challenging task requiring specialized knowledge. This is especially true for groups with many species, such as diatoms. Species identification may not seem like an important skill, but it can be thought of as an essential part of “ecoliteracy.” It is difficult to care about something if you do not know its name, and it can even become extinct without your knowledge.

As part of my Ph.D. research, I was able to do an in depth study of some of the diatoms in the Everglades, and described them as new species. Two of the species are in the genus Mastogloia. Mastogloia calcarea is very abundant, while a similar diatom, Mastogloia pseudosmithii, is quite rare. Rare diatoms are difficult to study, because one image of a single diatom is not enough to understand how the cell morphology of that species changes through the life cycle of its population. To adequately describe the species, a researcher would have to wait until enough specimens could be found or happen to obtain a sample with a larger population of the rare diatom. Fortunately, I was able to find enough specimens of the rare diatom because my advisor, Evelyn Gaiser, has been collecting diatoms from all over the Greater Everglades as part of a large monitoring and research program since 2005. Even in samples with a “good” population, M. pseudosmithii was only 1% or less of the total diatom abundance. I found this species in samples usually from brackish areas near the coastal marshes of the Everglades, which have higher salt and phosphorus levels than areas in the interior of the Everglades.

Fig. 2. A size diminution series of Mastogloia pseudosmithii (Source: https://westerndiatoms.colorado.edu/taxa/species/mastogloia_pseudosmithii).

You can see in the collection of specimens in Fig. 2 that, as M. pseudosmithii becomes smaller with cell division, the ends of the valve changes from rostrate (pulled out like a nose) to rounded. You can also notice that the second and last images are actually part of the same cell as the specimen to their immediate left. The structures indicated by the arrows in Fig. 2 are the partectal rings, a special girdle band that all species in the genus Mastogloia possess. The partectaare chambers inside the diatom cell that are associated with the production of mucilage, which may protect the cell from drying out.

Fig. 3. Live cell of Mastogloia calcarea with mucilage strands originating from partecta.

Diatoms are sensitive indicators of environmental change, but using these or other algae as indicators is difficult if they are not identified correctly. To obtain accurate signals from diatoms about environmental conditions, researchers strive to put correct names (or at least, consistent names) to diatom species. Diatoms of the United Statesis a reference on North American diatoms (including Canadian records) with the goal of improving the use of diatoms in biomonitoring programs in the US.

Learning to identify diatoms can be a fun challenge when combined with the field station experience! This summer, I am co-instructing the college/graduate level Ecology and Systematics of Diatoms, as well as the high school level College Prep Diatoms at Iowa Lakeside Lab. The courses provide an immersive setting, excellent microscope station for each student, and fun sample collection field trips to local lakes, streams, and wetlands. Spread the word!

Fig. 4a. College Prep Diatoms students sampling river diatoms.

Fig. 4b. Sharing diatom knowledge at College Prep Diatoms.

Tags # Diatoms # Taxonomy Continue Reading